<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>id选择器</title>

    <style>
        #pink {
            background: blue;
            width: 250px;
            height: 250px;
        }
    </style>
</head>

<body>
    <div id="pink"></div>
</body>

</html>